Light weight concrete and polystyrene pellets don't have much in common. Most light weight concretes are complex and replace the aggregates with something lighter. Usually something like gypsum, perlite or whatever. Basically a very complex subject, not many new practical mousetraps being invented every day, week, month or even year.

A science of additives, materials,methods, placement and techniques. Get any one of them wrong and it can bite you. The Romans probably understood it as well as anyone.

BTW... This idea of air entrainment in concrete has little to do with making it lighter. As I said very complex, better to research why fly ash works as an additive. Air addition has a place, it is not any sort of a magic bullet. Many things work, but as techniques that are both well understood and implemented, at both an engineering and workman level.

We bought a case of packing pellets from U-haul that are pure corn starch. When you're done with them (and don't want them anymore) you just wet them and they melt down to their original form (whitened water). Much more enviro friendly!